tiny529

Ugh... My brain is fried on this stuff. Since this was a multiple guess, I just guessed until I guessed right. I'll worry about understanding it when we get to that chapter. We're still in the middle of learning about carboxyls... Not even close to carbohydrates yet. I did end up completing them all, amazingly enough. I just hope my prof doesn't decide to spring even more problems on us since my trial period is up in just a couple of days. Good thing I'm not taking a lab... I can't go ballistic and blow up the chemistry department if he does add more problems...

Yeah, that's exactly what my pictures look like. I've got 4 different ones and I have to say which ones are chiral. I understand that to be chiral, the carbon needs to have 4 different substituents, but the way I see it, all of the carbons except for C1 have 4 different substituents. =\ But all 4 isn't one of the multiple choice choices. I forgot to note that it's the product of the carbohydrate after being treated with HNO3 that needs to be chiral.

None of the above... =) We are given 4 different unnamed structures and are told to mark which ones have optically active carbons. They are all in chair form and show the -OH groups as either axial or equatorial. I haven't learned any of this material and it seems rather foreign. The other chapters that I haven't done yet at least still made sense, even if it was new material. This carbohydrate stuff is really confusing. =(

Okay... Stereochemistry has never been my strong point, so seeing all of this chiral stuff in the carbohydrates chapter is kind of freaking me out. My book is confusing the heck out of me. Is there any trick to figuring out optically active carbons in a carbohydrate ring? Only 4 problems left, BTW... Out of 80 problems covering 8 chapters, 3 of which I haven't even done yet. The chirality is a multiple guess problem, so if worst comes to worst, I'll just... guess. I've got 3 "guess the product/intermediate" problems left but I don't have it in me to try them tonight. Tomorrow is another day! I'm going to bed.

Valine! Yay! Thanks! I'm sure that this is just the beginning of my questions. I've got 28 more to do by the weekend and they are ALL on chapters that we haven't dealt with yet. =(

Here's another one... =) An unknown amino acid was treated with ninhydrin in -OH/H2O. On completion of the reaction, a compound that gave a positive Tollens test was isolated from the product mixture. Its 1H NMR spectrum exhibited resonances at 1.10 (d, 6H), 2.20-2.60 (multiplet, 1H), 9.60 (d, 1H) ppm, and three distinct signals were present in its 13C NMR spectrum. Draw the structure for the unknown amino acid. Do not draw the zwitterionic form. Now, I drew 2-amino-2-methylpropanoic acid as the unknown. I figured that would give 2-methylpropanal when treated with ninhydrin. That would give a positive Tollens test, three 13C NMR signals, and the appropriate 1H NMR signals. Am I missing something? This program HAS marked some of my structures wrong that weren't wrong. I actually drew one of them 4 times (I was 100% sure that I was right!) before it took it. =\

Yep, that's what I finally ended up with. =) Now I've got a new question, which I'll put in a new post... =)

Yeah, I got acetone and a diol. If I give the diol as my answer, it tells me that I'm on the right track, but how can it react further. The annoying thing is that I asked my prof today and he said that my answer was right. He said nothing about reacting it further. I tried reacting it further to lose water and give a cyclic ether, but it didn't like that answer either. Okay... Just tried it yet again and got a lactone. It seemed to like that answer.

Hello again! I'm back with another Orgo 2 question. My prof has set up some online homework questions that require a registration code that came in the shrink wrap of the textbook. Not knowing that I'd need to keep the stupid shrink wrap, I tossed it and am forced to do a whole semester's worth of homework in 4 days as I'm on a "free trial". That being said, I might have a bunch of questions between now and the weekend. I've done 4 chapter's worth of the homework so far, but I'm stuck on the last problem of the 5th chapter. Haven't even looked at the other chapters yet. *mutter* So here's my question... First off, I'm not 100% sure of the name of the starting compound. My best guess is 3,3-dimethyl-2,4-dioxane-ethanoic acid. Anyway, that needs to be treated with H2SO4 in water. I'm supposed to draw the resulting product. I have no idea how to go about doing this. My 1st guess was just the starting product, figuring that the acid would hydrate the carboxylic acid, but that it would lose water and end up back where it started. That was, obviously, wrong, but it did tell me that I need to do hydrolysis of a ketal. When I work that out on paper, I get 2 products, but this is only asking for "the expected product". Can anyone lend me some insight??? Thanks in advance... =) Here's a picture of the problem...

I have no idea what any of that is. =b I did check webbook.nist.gov/chemistry and the tert-butylbromide MS doesn't match the quiz... 2-bromobutane does. It's only 1 point, but I'm getting a little anal in my old age. =)

Unfortunately, my answer was wrong... The correct answer was 1,3-dichlorobutane. Still doesn't match the C NMR, but it does match the H NMR better than mine does. Thanks for the help guys! I'm sure I will be back soon enough with more annoying undergrad OChem2 questions. Still waiting to hear back from my prof about a problem I think he had wrong... Correct me if I'm wrong, but tert-butylbromide will not show any molecular ion on a mass spec, right? I gave the answer of 2-bromobutane, but he marked it wrong.

According to my textbook (granted, I think my textbook is crap), aniline treated with NaNO2 and HCl will form the diazonium ion and an azo compound (though the yield is low). Sorry... I guess I tend to assume that everyone on here is doing this primarily on paper. =)

This problems seems a little mean anyway. =) If it were just the H NMR, I'd be fine. It's the C NMR that's throwing me off so badly. =\ I'm a senior at Temple. The kicker is that I haven't had Organic Chemistry 1 in about 10 years. This is the only class standing between me and my BS (which is partly why it's taken me 10 years to get back to it...) I've been studying on my own since about August, so I feel as comfortable as I can with the subject. I got a 100% on my last quiz, I am grasping most of it. Amazingly enough, I'm actually starting to enjoy it (something I never thought I'd say!), though this particular problem is making me want to pull my hair out.

There is one more thing I'm noticing about the H NMR... The triplet @ ~3.7 isn't in a 1:3:1 ratio. Just eyeballing it, it looks like 1:4:3, which doesn't make any sense... Could that possibly not be a real triplet? I'll keep plugging away for now, but if I still haven't come up with anything by tomorrow night, I'll use 3,3-dichloro-2-methylpentane and hope that my prof gives partial credit if it's wrong.

Brain fart on my part... Sorry about that. I was looking at C3 as a quaternary simply because it had no hydrogens attached. Wasn't thinking about the fact that it it didn't have carbons attached on all sides. =\ Also, there isn't a quaternary carbon showing at 30 on the C NMR? I'm confused... ='( Just assumed that these were software. What is COSY, HMQC, and HMBC? Will try doodling a little more, but I'm starting to reach my boiling point with this one. It's worth 20% of the quiz grade though so I can't just let it go. Does anyone have any ideas? Something that I am missing???